The invention relates to a method and apparatus for providing a substrate such as a textile fabric or a paper sheet with a mesh-like pattern of reinforcing plastic stripes or strands. The invention has particular usefulness for reinforcing paper used for manufacturing articles-carrying paper bags.
Carry-out paper bags are convenient to assist customers in carrying out purchases made from grocery stores, market stores, liquor stores, hardwares and the like. The inconveniences of ordinary carry-out paper bags are many and well-known. They have limited load carrying capacity, they are easily punctured or torn by the sharp corners of the articles carried and, if exposed to wet or sweating surfaces, they tear very easily. The load carrying capacities or ordinary paper bags are so poor that it is often best to place two or more bags within each other before filling them with heavy articles, such as bottles and the like, and it is a good precaution for the customer to carry a loaded bag by holding it under its bottom panels rather than by grasping it at the top of its side panels.
It would therefore be advantageous to provide ordinary carry-out bags made of paper, such as the kraft or sulfate paper commonly used for making such bags, with a greatly improved load carrying capacity without substituting heavy-weight for light-weight kraft stock, without resorting to using two light-weight kraft paper blanks formed together in the form of a multi-layer bag called a "Duplex" bag, and without being subjected to almost immediate self destruction when wet.
Attempts have been made in the past at reinforcing paper or at providing reinforced paper shopping bags. For example,in U.S. Pat. No. 3,248,041 there is disclosed a reinforced multi-wall bag, in U.S. Pat. No. 2,653,090 there is disclosed a glass strand reinforced paper, and in German Patent Publication No. 2,263,624 there is disclosed a bag provided with reinforcing extruded plastic strands arranged laterally across each side of the bag proximate the carrying handle attached to the top of each bag side.
It is readily apparent that a reinforced multi-wall bag is relatively complex, costly to manufacture, and offers no savings in the tonnage of paper used for manufacturing a given number of bags, that duplex bags made of two light-weight kraft paper sheets formed together in the form of a bag do not provide improved strength as compared to a bag made of a single sheet of heavy-weight kraft paper, that glass strand reinforced paper wherein, the glass strand is embedded in the center of the mass of paper fiber, requires that the glass strands be first made and be subsequently immersed in the paper pulp during the paper manufacture operation, and that forming reinforcing strands in a lateral direction across the sides of a bag has very little effect on increasing the load-carrying capacity of a paper bag, especially when wet.
In copending application Ser. No. 88,863, filed on the same day as the present application, there is disclosed a plastic reinforced paper which is obtained without changing paper making techniques, without modification of paper making machinery other than the addition of the relatively simple and low cost plastic reinforcement applying unit for practicing the method of the present invention, without modification of bag making machinery presently existing, and without reduction in production rate. By using the reinforced paper disclosed in the aforementioned application, paper bags having a substantial load-carrying capacity can be made from a substantially light-weight kraft paper, thus considerably reducing the tonnage of raw material and the energy cost required for manufacturing paper bags.